Many applications exist for high speed valves and switches such as circuit breakers and other safety related devices that must respond quickly to prevent catastrophic equipment damage. Some of these applications may have relatively large moving masses that are difficult to move quickly because of the large forces needed.
Prior art, such as Lissandrin, U.S. Pat. No. 5,187,339, uses pneumatic pressure to move a piston, but piston acceleration is limited by the pressure used and the speed at which the gas can flow into the piston's cylinder. Prior art such as Imam, U.S. Pat. No. 4,384,182, use hydraulic pressure to move a piston, but like pneumatically driven devices, the speed is limited by pressure and the speed of the driving fluid.
Yet other prior art, such as Ford et al., U.S. Pat. No. 4,174,471, Niemeyer, U.S. Pat. No. 4,345,127, Schroder, U.S. Pat. No. 4,311,890, and Simonsen, U.S. Pat. No. 4,244,487 achieve great speed through the use of explosive charges, but are limited to one-shot applications because the device is destroyed upon actuation.
Actuating devices intended for repetitive operation must survive each actuation without damage. The moving parts of fast acting devices must be accelerated to relatively high velocities and thus acquire substantial kinetic energy that must be absorbed to bring the parts to a stop in the actuated position. Consequently, once the moving parts have achieved the needed velocity, the accelerating force must be replaced with a decelerating force. Prior systems make no provision for quickly removing the accelerating force and simply allow the moving parts to strike a fixed mechanical stop. While prior methods work without problems when velocities are relatively slow, at high velocities a fixed mechanical stop results in severe stresses that cause permanent deformation and store energy in a spring like action. Neither severe permanent deformation nor spring action are acceptable as repeated deformation causes the parts to fracture, while any spring action causes the moving parts to bounce back toward the initial position with little loss of kinetic energy. Without some provision for quickly removing the accelerating force and absorbing the kinetic energy, destructive forces will destroy a mechanical stop.
While a variable orifice hydraulic shock absorber intended to bring a moving mass to a stop can be used, prior art in these devices such as Dressell, Jr. et al., U.S. Pat. No. 4,298,101, are not intended to operate at the velocities needed for speeds that approach that of explosively actuated devices. It would be difficult to provide orifices large enough to prevent excessive hydraulic pressures from being generated.
Needs exist for high speed valves and switches that respond quickly to prevent catastrophic equipment damage.